High viscosity index lubricating oil



April 6, 1954 J. G. LILLARD HIGH VISCOSITY INDEX LUBRICATING on FiledJuly 26, 1950 m 7 v 6 E I I w v [I L j I I a 8 M E I5 I B M M w A III Hm L H N u :0 3 M A I R Ii M 4 1-- H 4. N \I 6 M E II I I 5 I EM" mu 9 m2 u I I l l I I I I I I I I I I I I I I I I I I IL 1|| 2 r IIL. u H u yIn M m 2 5 5 4 4 T I II I N ll 7 L I 4 8 o 4 S .Il R A I- 0 P E e u M A0 m T II T I I. s s W I H w J9 m v a 3 n 2 L 4 3 4 I 8 4 3 5 3 7 M 3'l-Illl 2 6 3 3 8 2 n I n G L LOW VISCOSITY INDEX l VERY LOW VISCOSIT YINDEX HIGH VISCOSITY INDEX LOW VISCOSITY INDEX IN VENTOR.

Patented Apr. 6, 1954 James G. Lillard, Baytowng Tc'x.; assignor, by-

mesne assignments, to StandardnOiI Develop--v ment Company,- Elizabeth NJ of Delaware a corporation 5 Application July 26, 1950, Serial No.176,003 1 Claim: (Cl. 196151) Thepresent invention may be describedbriefly as a high viscosity index lubricating oil composttioncontainingonly components which will allow the composition to have a high:viscosity index. Thecomposition of the present invention consists of amixture of 'paraffinic naphthenes and aromatic naphthenes boiling in thelubricatingoil boiling ranger thenes to aromatic mately -7':1.'

Paraffinic and-aromatic naphthenes employed in the lubricating oil ofthe present invention may 'be characterized by the following formula-:

M(n -l.4750),- 8*

in which M is theaverage: molecular weight and The ratio of paraffinicnaphnaphthenes may be approxin is i the index of refraction at 20, F. ofsaid:

naphthenes using the sodium D. line." The. nue meral *l.4750 is-obtainedby plotting-"the reciprocal of th"e-molecular--weight of a: largenumbenofhydrocarbons of T different typessagainst the refractive index ofthese hydrocarbons to obtain Each type of :'hydro-I-- carbon will"follow along a separate-straight line 1 but all h'ydrocarbons of thesame:=type..will:fol1ow:

a series of straight lines.

in the-same line.- to one anotheran'd These :linesware not parallelwhich they converge. forinfinite-'molecular welght occurs atarefractive" index of -1.4750

It has been observed that 'the various hydro carbonsin lubricating oilfractions have factors; as determined from which vary widely. Generally,th'at paraffins have values (F)" or factors determined from theforegoing equation substantially rule ":above 8 while the have highviscosity indexes while those fractions having'F factors or aviscosityindexes:

It has been found that lubricating oil may be: separated 'bysilica :gelpercolation into. about 5- fractions-having: widely different viscosityindex:

*fRihg Analysis of Hydrocarbon Mixtures, Report PRL'448,issuedby'-the-Petro1eum Refining Laboratory; The, Pennsylvania: State College,State- Collcge,. Pa. June 7,1948.

may-be extended to a .point: corresponding to infinite molecular weightat: The point offl convergence when' using-the D line of: sodiumat atemperature of hydrocarbons of the foregoing equation,-

it has been found value above 8 havev low characteristics.- Thesevarious fractions each.

consist of a largenumber of compounds ofa certain type.' Silica gelpercolation separates as a first fraction of lubricating oil aparafiinic- A naphth'ene fraction containing from 1 to 3 naphthenerings, aromatic-naphthenes containing con aromatic and '1 naphthenicring;

the average 1 and condensed naphthenes-containing 2 or more naphthenerings, nap hthalenes containing 2 or more aromaticrings of which only 2are condensedwand higher condensed aromatics containingy3 or morearomatic rings of which at least 3 are condensed-.-

The paraffinic naphthenes may be considered as parafiinicand naphthenicfractions, whereas the aromatic naphthenes may-be considered as singlering aromatic fractions whichhas a naphthenic ring attached-thereto, asdescribed by Watson et al. in Patent 2,643,217, issued June 23, 1953,where identical compounds are described; Terminology of a-similar'naturgis described by Rossini in 'Refiner and Natural GasolineManufacturer,vol. 17, No.11, November, 1938.

When F factors or values for these various compound types'are obtainedfrom lubricating oil, for example, by silica gel percolation thereof;

thecompounds areseparated'largely as shown in' the following table:

Table I Compound Type F W Paraffinic Naphthenes 4 to +6 CondensedNaphthenes 8 to 10. Aromatic Naphthenes 2 to 6. Naphthaleues a. 10 to20. Higher Condensed Aromatic Greater than 40.

Inemploying the-F value to characterize. the various components in for aparticular stock assuming a constant molecular weight for. thelubricating oil fraction forwhichthevalue is to be obtained. Sinc thevmolecular weights of the narrow fractions secured by silica gelpercolation of the lubricating oil fraction have a max:- imum variationof'about 10 the F factor may have a maximum variation of about 10% dueto the molecular .weight change.

The paraffinic-naphthenes and: aromaticnaphthenes forming thecomposition of the present invention may be blended together in.any'ratio to give the desired viscosity index. However, since both the alubricating oil fraction it may be determined by paraffinic-naphthenes Jand" the 'aromatic-naphthenes have high vis- 1 cosity indexes ascompared to the low viscosity indexes of the other components of thelubricating oil, it will be desirable to utilize all of thearomatic-naphthenes with the paraflinic-naphthenes obtainable from agiven lubricating oil fraction. It has been determined that theparaffinic-naphthenes and aromatic-naphthenes are present in lubricatingoil fractions from the Panhandle field in Texas and from the TexasCoastal crudes in the approximate ratio of '7 parts by volume ofparaflinic-naphthene to about 1 part by volume of aromatic-naphthene.While this is the preferred ratio, it will be understood that greateramounts of the parafiinic naphthenes may be used depending on theviscosity index of the particular aromatic-naphthene secured from aparticular lubricating oil.

In order to illustrate the invention further, lubricating oil fractionsobtained from Panhandle crude from the Panhandle field in Texas and fromTexas Coastal crudes were subjected to contact with a column of silicagel. The lubricating oil fractions from the Panhandle crude were adewaxed medium motor oil distillate and a finished Bright Stock. Thedewaxed motor oil distillate on percolation through the column of silicagel gave the following results:

The data in the foregoing table show the percentage and the viscosityindex of the various fractions. It will be noted that theparaffinicnaphthenes have a viscosity index of 124 whereas 1 thecondensed naphthenes have a viscosity index of only 47. On the otherhand, the aromaticnaphthenes have a viscosity index of 9'7. Both ofthese fractions, therefore, are suitable for blending together to formthe composition of the present invention. It will be noted that theratio of paraffinic naphthenes to aromatic naphthenes is 7 /2 :1;consequently it is desirable to blend the paraifinie naphthenes with thearomatic naphthenes in this ratio to obtain maximum yields.

The parafiinic-naphthenes in Table II contain 1 to 3 naphthene rings.The condensed naphthenes contain 3 or more rings, at least 2 of whichare condensed, while the aromatic naphthenes contain on the average 1naphthene ring and l aromatic ring.

A finished Bright Stock from Panhandle crude was also percolated througha silica gel column and was found to contain 60% by volume ofparafimic-naphthene having a viscosity index of 109. The Bright Stockalso contained 8% by volume of naphthenes having a viscosity index of97. These fractions may also be blended to obtain a composition inaccordance with the present invention.

A medium motor oil distillate from a Texas Coastal crude was alsopercolated through a silica gel column and was found to contain 57% byvolume of paraffinic naphthenes and 7% by volume of aromatic naphthenes,the parafiinic:

naphthenes had a viscosity index of 102 while that of the aromaticnaphthenes was somewhat lower. In thi particular instance, it will benoted that the ratio of paraifinc naphthenes to aromatic naphthenes isnot quite 7 :1. It will be desirable, therefore, to blend theparafiinicnaphthene the aromatic-naphthenes in this particular ratio.

It has been mentioned that the composition of the present invention maybe obtained by percolating a lubricating oil fraction through silica geland blending the segregated fractions. The segregation of a lubricatingoil fraction into components of varying viscosity index characteristicsby means of silica gel may be carried out on a batch or continuousbasis. The optimum ratio of hydrocarbon oil to silica gel for a batchoperation is well known. a value of 1:10 by volume being typical. Thesilica gel i charged into a column whose ratio of diameter to length isgoverned by the degree of separation desired. For the type of separationdescribed in this memorandum, a ratio of diameter to length of 1:300 ispreferred.

The temperature at which the percolation is conducted may be atemperature in the range of about to about 150 F. A temperature of F.will give quite satisfactory results, if the viscosity of the oil isreduced by dilution with a light paraflinic solvent, such as normalheptane.

The invention will be further illustrated by reference to Fig. 1 inwhich a mode is described allowing the segregation of the high viscosityindex fractions necessary to provide the composition of the presentinvention, and

Fig. 2 wherein the composition of a given lubricating oil is showngraphically with reference to the composition of the present invention.

The segregation of a lubricating oil fraction into fractions of varyingviscosity index characteristics and recombination of certain fractionsto obtain an oil of improved viscosity index is illustrated in Figure 1.Column I0 is filled with silica gel. The quantity of oil, which isoptimum for the amount, of silica gel placed in column ID, is withdrawnfrom hydrocarbon charge tank II by means of pump l2 through line l3 andvalve l4 and discharged into charge blending tank l5. After valve [4 isclosed, paraffinic solvent is withdrawn from tank l6 by pump I? throughline l8 and valve I9 until the desired ratio of paraffin solvent to oilfor control of the viscosity of the mixture is obtained.-

Valve I9 is then closed and connected to controller 20 which keeps it ina closed position until activated by liquid level control 2|. It is notnecessary that the oil and paraflinic solvent be mixed in a tank beforecharging them to the silica gel column; if it is more convenient, thetwo may be continuously pumped in the proper ratio into a linecontaining go directly from the incorporator into the silica gel column.After the hydrocarbon and paraffin solvent have been thoroughly mixed bymixer 22, valve 23 is opened and the charge passes from the chargeblending tank through pump 24 into the silica gel column. Before valve23 is opened, valves 24A and 26 are closed and outlet valve 25 isopened. As the mixture of hydrocarbon and paraflin solvent passesthrough the silica gel, it is separated into various fractions,depending upon the afiinity of the silica gel for the various compoundtypes. The order of increasing affinity of silica gel for the vari ouscompound types is: paraifinic naphthenes,

an incorporator and aiergoes finic solvent under" the-condition beingde* scribed. The 'efllue'nt from the silica gel column In passes throughline}? and valve 25 where it is pumped by'purnp'zs intofractionatingcolumn 29. This column causesa. separation between the hydrocarbon andtheparaflinic solvent admixed with it. The paraffinic solvent is takenas overhead'through line 3fl-and pumped into the-*paraffinic solventstorage tank-I B. The hydrocarbon' is withdrawn as bottoms through line3| and all; or a portion of it, passes through a refractive indexincheating-recording device 32. The signal from the refractiveindexindicator is transmitted through line 33 into recorder 34 whichconvertsdt"int'o"'an'F"value. The recorder' '34 is adjusted for the imolecular "weight of the lubricating oil being-percolated lar narrowlubricating oil fraction" recovered from column I will not varygreatly,the F value will not be effected substantially by any: slight variationthereof. If the F value is 8 or greater, a signal is transmitted throughline 35 to valve 36 causing it to open and through line 40 to valve 4|causing it to close; the material is discharged through line 31 and pump38 into tank 39 which contains the lower viscosity index fractions. Ifthe F factor is less than 8, a signal is transmitted through line 40 toopen valve 4| and through line 35 to close valve 36. Thus, material forwhich F is less than 8 is passed into tank 42 through line 43. This tank42 contains the higher viscosity index components of the lubricating oilfraction. When the charge contained in the charge blending tank I isdepleted, liquid level control 2| causes valve 20 to be opened and aparaiiinic solvent is pumped through the charge blending tank into thesilica gel column HI. This solvent flushes remaining materials for whichsilica gel does not have a relatively strong affinity from column Ininto fractionator 29. When the paraifinic solvent no longer desorbsappreciable quantities of material from the silica gel in column Hi, theliquid level in column 29 decreases and causes liquid level control 44to close valve 23, open valve 24A, close valve 25, and open valve 26.When the valves are positioned in this manner, a polar solvent such asbenzene or alcohol is withdrawn from tank 45 and forced into silica gelcolumn H] by pump 46 to cause the material remaining adsorbed on thesilica gel to be desorbed and pass out of the column l0 through line 21and valve 25 and be pumped into fractionator 41 which effects aseparation between the polar solvent and the material which it hasdesorbed. When desorbing the silica gel in column In with a polarsolvent, the output of the column l0 does not pass through a refractiveindex determining device because it has been found that all hydrocarbons that have to be desorbed from silica gel by using a polarsolvent have F factors considerably greater than or 15. Therefore, allof the material desorbed by the polar solvent will have undesirablelower viscosity index characteristics. When the silica gel in column IIIhas been completely desorbed as indicated by liquid level indicator 43,all valves are closed and the silica gel is regenerated. Thisregeneration may be car ried out in the silica gel column H] by any onemamma -"naphthenes: naphthalenes, and highencondense'd aromatics;

in 'coliim'n' I0. Since the molecular weight of the-particu-' of severalmethods such as by blowing with steam The facilities "for "the'regeneration described since they are well known to the art.In-somecaees it may or hot-air. operation are not shown or be preferabletodiscard the spentsilica gel and recharge thecolurnn with fresh silicagel. As a matter' of convenience, a second column may with the firstcolumns'obe connected in parallel that another chargeof' hydrocarbon andparaffin solvent may be passed through this second column while *thefirst is being regenerated. operate more than one silica gel columnwiththe same auxiliary equip equipment for the segre gation of thehydrocarbon into the desired'vls Thus, it is possible to ment and thenecessary cosity index components is simplified.

The action of column |0 control of its operation by referring to Fig.2'wherein the various shaded bands indicate different volume per centbeing taken at the right. The area 49 represents theparafiinic-naphthenes fraction, 50 represents the condensed naphthenesfraction, 5| represents the aromatic-naphthenes fraction, 52 representsthe naphthalenes fraction, and the shaded area 53 represents the highercondensed aromatics fractions. The viscosity in dex characteristics ofthese various fractions is indicated within the rectangle representingeach fraction. The line 54 indicates the separation usually obtained byphenol extraction, the material below the line being that extracted bythe phenol. Increasing the severity of a conventional phenol treatcauses the central portion 55 of the line 54 to move to the left, thusextracting more of the low viscosity index fraction 50 and also of thehigh viscosity index fraction 5| with the total effect being to increasethe viscosity index of the material not taken up by the phenol. In thesame manner decreasing the severity of the phenol treat causes thecentral portion 55 to move to the right which not only causes more ofthe high viscosity index fraction 5| to be included in the raflinate,but also includes more of the low viscosity index fractions 50'and 52,thus decreasing the total viscosity index of the material not taken upin the phenol. The present method of separation controlled by thecharacterization factor F does not allow these various fractions to besmeared into one another, and, thus, at all times allows a sharpseparation of the high and low viscosity index components. The line 56separating fractions 5| and 52 is the natural cut point for compoundsadsorbed on silica gel between the desorbing powers of paraffinic andpolar solvents, with the material to the left of this line being removedfrom silica gel by paraffinic solvents, and the material to the right ofthe line requiring polar solvents for elutriation.

From the foregoing description taken with the two figures, it will beseen that two components of the lubricating oil of the present inventionmay suitably be obtained by silica gel extraction. The lubricating oilmay be separated into paraffinic-naphthenes and into aromatic-naphthenesby extraction with solvents but this may be a tedious, time-consumingoperation.

In obtaining the paraflinic-naphthenes and aromatic-naphthenes for thelubricating composition of the present invention, it is desirable to incombination with' by means of the char acterization factor F maybe-readily understood silica gel fractions from a'lubricating oil. Thehorizontal axis of the bar represents the volume per cent distributionof the hydrocarbon fraction, with zero volume per cent being taken inthe left of the figure'and' extract untreated lubricating oil fractions.Otherwise, if a lubricating oil is subjected to a treatment withsulfuric acid such, for example, as practiced in the petroleum refinery,or to contact with clay, such as Super Filtrol or other types well knownin the refining industry, there is danger that the aromatic-naphthenesmay be lost either by chemical action or by physical adsorption. Whileit is desirable to work with the total or untreated lubricating oilfraction, it is within the purview and scope of my invention to workwith solvent extracts or raffinates which contain paraffinic-naphthenesand aromaticnaphthenes for segregation thereof for use in thecomposition of my invention.

The nature and objects of the present invention having been fullydescribed and illustrated, what I desire to claim as new and useful andto secure by Letters Patent is:

A lubricating oil composition consisting of a mixture of approximately 7parts of a paraffinio and naphthenio fraction having from 1 to 3naphthene rings and approximately 1 part of single ring aromaticfraction having an average of one naphthene ring and one aromatic ringboiling in the lubricating oil boiling range, said.

fractions being characterized by the formula M (n 1.4750 8 where M isthe average molecular weight and n is the index of refraction at 20 F.for the sodium D line of said naphthenes, said fractions havingviscosity in dexes of 102 to 124 and 97, respectively.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Refiner and Natural Gasoline Manufacturer, vol. 17, No. 11,Nov. 1938, pages 557-567 inclusive (Rossini).

Indust. and Engineering Chemistry, vol. 39, No. 12, Dec. 1947, pages1585-1596, inclusive (Hirsch ler et al.)

